Flexible package

ABSTRACT

A flexible package including a package body including a first side-surface film and a second side-surface film sealed in a peripheral portion. The package body has sealed portions formed in side edge portions such that a non-sealed portion is formed in at least one of the sealed portions. The non-sealed portion has a gas injection portion containing a gas which has a specific heat at constant volume of 0.67 kJ/kg·deg or higher at 0° C. and 1 atm. The gas injection portion has a diameter of from 3 to 50 mm and is formed such that a repelling force is from 4 to 30 N at 23° C. and 1 atm when an entire gas injection portion is nipped from both sides of the first and second side-surface films and squeezed until a nipped gas injection portion has a width equal to a half of the diameter of the gas injection portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of Ser. No. 14/803,943, filedJul. 20, 2015, which is a continuation of International Application No.PCT/JP2014/000351, filed Jan. 24, 2014, which is based upon and claimsthe benefits of priority to Japanese Application No. 2013-012073, filedJan. 25, 2013, Japanese Application No. 2013-136467, filed Jun. 28,2013, Japanese Application No. 2013-136468, filed Jun. 28, 2013,Japanese Application No. 2013-136469, filed Jun. 28, 2013, JapaneseApplication No. 2013-136470, filed Jun. 28, 2013, Japanese ApplicationNo. 2013-136471, filed Jun. 28, 2013, and Japanese Application No.2013-172171, filed Aug. 22, 2013. The entire contents of all of theabove applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a flexible package.

2. Discussion of the Background

As a package for packaging contents such as liquid, a viscous substance,powder, a solid, or the like, a flexible package formed by joining filmstogether and sealing peripheral portions of the films has been known.

As disclosed in Japanese Laid-Open Patent Publications No. 8-119294 andNo. 2004-256126, a flexible package is, for example, a pouch whoseself-standing property is improved by devising the shape of a bottomsurface or the shapes of a bottom surface and a side surface. A bottomgusset type pouch is widely used which is produced by inserting, at abottom portion of a laminated film (barrel member) having both front andrear surfaces, another laminated film (bottom member) that is folded,and heat-sealing both side edge portions and a bottom edge portion. Aflexible package filled with contents and having a sealed opening can bedisplayed or used on a table, and therefore, is widely used as aresource-saving package substituting for a rigid container.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a flexible packageincluding a package body including a first side-surface film and asecond side-surface film sealed in a peripheral portion such that astorage portion is formed in the package body. The package body hassealed portions formed in side edge portions such that a non-sealedpotion is formed in at least one of the sealed portions. The non-sealedportion has a gas injection portion containing a gas which has aspecific heat at constant volume of 0.67 kJ/kg·deg or higher at 0° C.and 1 atm. The gas injection portion has a diameter in a range of from 3mm to 50 mm and is formed such that a repelling force is in a range offrom 4 N to 30 N at 23° C. and 1 atm when an entire gas injectionportion is nipped from both sides of the first and second side-surfacefilms and squeezed until a nipped gas injection portion has a widthequal to a half of the diameter of the gas injection portion.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a plan view of a flexible package.

FIG. 2 is a cross-sectional view of the flexible package.

FIG. 3 is a plan view of a blank of the flexible package.

FIGS. 4( a)-4(c) are schematic diagrams illustrating a method of fillingthe flexible package with gas.

FIGS. 5( a)-5(c) are schematic diagrams illustrating a method of fillingthe flexible package with gas.

FIGS. 6( a)-6(c) are schematic diagrams illustrating a method of fillingthe flexible package with gas.

FIG. 7 is an enlarged schematic diagram illustrating a method of fillingthe flexible package with gas.

FIGS. 8( a) and 8(b) are cross-sectional views of a gas injectionportion of the flexible package.

FIG. 9 is a schematic diagram illustrating a method of measuring loopstiffness.

FIG. 10 is a schematic cross-sectional view of a laminated structure ofa gas barrier film.

FIG. 11 is a plan view of a flexible package.

FIGS. 12( a) and 12(b) are diagrams illustrating a method of discharginggas from the flexible package.

FIG. 13 is a partially enlarged view of a flexible package.

FIG. 14 is a plan view of a flexible package.

FIGS. 15( a) and 15(b) are partially enlarged views of the flexiblepackage.

FIGS. 16( a)-16(c) are partially enlarged views of the flexible package.

FIG. 17 is a plan view of a flexible package.

FIG. 18 is a partially enlarged view of the flexible package.

FIG. 19 is a partially enlarged view of the flexible package.

DESCRIPTION OF THE EMBODIMENTS

The embodiments will now be described with reference to the accompanyingdrawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings.

(Summary of Flexible Package)

FIG. 1 is a plan view of a flexible package 100 according to anembodiment. The flexible package 100 is formed by joining a firstside-surface film 101, a second side-surface film 102, and a bottom film103 together. The bottom film 103 is inserted, with a predeterminedinsertion length, between the first and second side-surface films 101and 102 such that it is folded in half and inserted from the hold lineside. Peripheral portions of these films joined together, excluding aportion through which contents are to be injected, are sealed, therebyforming a storage part 105. Assuming that an end portion of the flexiblepackage 100, from which the bottom film 103 is inserted, faces adownward direction, the portion through which the contents are to beinjected is, for example, upper ends of the first side-surface film 101and the second side-surface film 102.

As a material of the first side-surface film 101, the secondside-surface film 102, and the bottom film 103, which form the flexiblepackage 100, for example, a laminate containing resin or aluminum,including a sealant layer at an innermost surface, and having a certainrigidity may be used. As an example of the laminate, there is a laminatehaving a layer structure of polyethyleneterephthalate/aluminum/nylon/low-density polyethylene in a directionfrom the outer side to the inner side of the flexible package 100.

An end portion in the left-right direction, of the region where theperipheral portions of the first side-surface film 101 and the secondside-surface film 102 are sealed, is referred to as a side edge portion108. In the side edge portion 108, a non-sealed region 106 is provided.The non-sealed region 106 is a region which is not sealed over apredetermined length in the top-bottom direction and is surrounded bythe sealed region. The non-sealed region 106 may be provided in eitheror both of the left and right side edge portions 108.

The flexible package 100 includes a discharge part 104 which is to beopened for discharging the contents. For example, as shown in FIG. 1,the discharge part 104 is formed by attaching a spout member between thefirst side-surface film 101 and the second side-surface film 102. Theshape and structure of the discharge part 104 are not limited thereto,and the discharge part 104 may be omitted.

The storage part 105 is, after the contents have been injected therein,is sealed by sealing the upper ends of the first side-surface film 101and the second side-surface film 102. When the bottom film 103 isexpanded so that the first side-surface film 101 and the secondside-surface film 102 form a cylindrical shape on the side where thebottom film 103 is sealed, the flexible package 100 is allowed to standby itself with the bottom film 103 being a bottom surface. FIG. 1 is aplan view of the flexible package 100 in this state, and FIG. 2 is across-sectional view taken along a X-X′ line in FIG. 1.

In the non-sealed region 106, gas is injected through a slit 111 toexpand the first side-surface film 101 and the second side-surface film102, thereby forming a gas injection portion 107. In a region where theslit 111 is formed, after the formation of the gas injection portion107, the first side-surface film 101 and the second side-surface film102 are sealed to prevent the gas from escaping through the slit 111. Ifthe slit 111 is positioned near an upper end of the non-sealed region106, the sealing to seal the storage part 105 and the sealing to sealthe portion near the slit 111 can be performed in the same process step.A production method for the flexible package 100 will be described laterin detail.

As described above, since the gas injection portion 107 is provided inthe side edge portion 108 of the flexible package 100, the firstside-surface film 101 and the second side-surface film 102 are lesslikely to bend at the gas injection portion 107 and its vicinity.Therefore, when the flexible package 100 is made to stand by itself, theoverall shape of the flexible package 100 is less likely to deform, andthus the self-standing property thereof is easily maintained. When theflexible package 100 is carried or when the contents are taken out, thefirst side-surface film 101 and the second side-surface film 102 aroundthe gas injection portion 107 serve as a handle. Therefore, a user caneasily hold the flexible package 100 by grasping the gas injectionportion 107. In the flexible package 100 according to the presentembodiment, excellent shape retaining property provided by the gasinjection portion 107 can stabilize the position of the outlet when thecontents, even if the amount of the contents is small, are taken out ofthe package 100, and thus discharge of the contents is facilitated. Whenthe flexible package 100 having the contents therein is heated in hotwater or a microwave oven, the storage part 105 of the flexible package100 becomes hot due to the heated contents. However, the user, holdingthe gas injection portion 107, can hold the flexible package 100 withoutfeeling hot.

(Production Method for Flexible Package)

Hereinafter, a production method for the flexible package 100 will bedescribed.

First, the first side-surface film 101 and the second side-surface film102, each having a sealant layer, are disposed so that the sealantlayers thereof oppose each other. The bottom film 103 having a sealantlayer is folded in half so that the sealant layer faces outside, and thefolded bottom film 103 is inserted between the first side-surface film101 and the second side-surface film 102 so that a fold line facesinside the first side-surface film 101 and the second side-surface film102.

Next, the peripheral portions of the first side-surface film 101 and thesecond side-surface film 102 are heat-sealed, excluding the non-sealedregion 106, a region where the discharge part 104 is to be attached, anda region to be an opening for injection of contents. Thereby, in theportion where the bottom film 103 is inserted, the first side-surfacefilm 101 and the bottom film 103 are sealed together, and the secondside-surface film 102 and the bottom film 103 are sealed together. Inthe portion where the bottom film 103 is not inserted, the firstside-surface film 101 and the second side-surface film 102 are sealedtogether, excluding the regions not to be sealed (i.e., the region to bethe non-sealed region 106, the region where the discharge part 104 is tobe attached, and the region to be an opening for injection of contents).In a region near the upper end of the non-sealed region 106,simultaneously with the heat sealing or at a time before or after theheat sealing, the slit 111 for gas injection is formed in one or both ofthe first side-surface film 101 and the second side-surface film 102.Further, simultaneously with the heat sealing or at a time before orafter the heat sealing, the peripheral portions of the firstside-surface film 101, the second side-surface film 102, and the bottomfilm 103 are cut, thereby to form these films in a desired plane shape.

Next, in the region where the discharge part 104 is to be attached, thedischarge part 104, which is separately formed, is inserted between thefirst side-surface film 101 and the second side-surface film 102, andoverlapping portions of the first side-surface film 101, the secondside-surface film 102, and the discharge part 104 are heat-sealed. Theattachment of the discharge part 104 may be performed simultaneouslywith the heat sealing of the first side-surface film 101, the secondside-surface film 102, and the bottom film 103. Through theabove-described process steps, a blank 120 shown in FIG. 3 is produced.

(Gas Filling Method)

FIG. 4( a) to FIG. 6( c) are diagrams illustrating a method of fillinggas in the non-sealed region 106 of the blank 120 shown in FIG. 3,simultaneously with the process step of filling contents in the blank120 and sealing the opening portion. The blank 120 is held at the bothside edge portions 108 thereof by a gripper of a well-known intermittentrotation type rotary pouch packaging device, is hung, and isintermittently transferred. At stop positions, the packaging steps suchas opening of the blank 120, filling of contents, sealing of the openingportion, and the like are sequentially performed.

As shown in FIG. 4( a), the blank 120 held by the gripper 10 is filledwith contents 11 at a contents filling position, and subsequently, isrotationally moved and stopped at a gas filling position (FIG. 4( b)),where a gas filling step is performed. In the gas filling step, a tip ofa later-described gas blowing nozzle 17 is applied to the slit 111, andgas is blown through the slit 111 into the non-sealed region 106.Subsequently, a portion directly beneath the slit 111 is heat-sealed(seal portion 12), whereby the non-sealed region 106 is hermeticallysealed to enclose the pressurized gas therein. Thereby, the non-sealedregion 106 (gas injection portion 107) in which the pressurized gas isenclosed is formed in the side edge portion 108 of the blank 120. In thegas filling step, simultaneously with the heat sealing directly beneaththe slit 111, the upper end of the blank 120 is linearly sealed to forma line seal portion 13. Subsequently, the blank 120 is rotationallymoved and stopped at a sealing position (FIG. 4( c)), where a sealingstep is performed. In this sealing step, the opening including the slit111 is flatly sealed to form a seal portion 14. At this time, theportion of the slit 111 may be fused to improve the appearance.

While in this example, the slit 111 is formed in the non-sealed region106 as the gas blowing part, a hole may be formed instead of the slit111. However, when a hole is formed, the fused films may adhere to aheating plate for sealing or overflow through the hole. Therefore, it ispreferable to form a slit like the slit 111 that prevents the abovedrawbacks. Further, in this example, the slit 111 is formed near theupper end of the non-sealed region 106, but the position of the slit 111is not particularly limited. However, when the slit 111 is formed nearthe upper end, gas sealing can be performed by sealing a portiondirectly beneath the slit 111. In addition, as shown in FIGS. 5( a)-5(c)described later, sealing of the non-sealed region 106 can be performedsimultaneously with line sealing which is usually performed, and areceiving member (heating plate) for the line sealing can be used.Therefore, the slit 111 is desirably formed near the upper end. Further,in this example, the sealing of the opening portion is performed in eachof the gas filling step and the sealing step (two times in total).However, sealing may be performed only in the sealing step whileomitting the sealing in the gas filling step, or sealing may beperformed only in the gas filling step while omitting the sealing step.

Next, the respective steps shown in FIGS. 4( a)-4(c) will be describedin more detail with reference to FIGS. 5( a)-5(c), 6(a)-6(c) and 7.FIGS. 5( a), 5(b) and 5(c) and FIG. 6( a) sequentially show the gasfilling step performed on the blank 120 (already filled with contents)stopped at the gas filling position, and the sealing step performed onthe blank 120 stopped at the sealing position. In the gas fillingposition, a heating plate 15 for line sealing of the opening, a heatingplate 16 for sealing of the non-sealed region 106, and a gas blowingnozzle 17 at an intermediate height between them are disposed on oneside, and a heating plate 18 as a receiving member is disposed on theother side across the blank 120. The heating plates 15 and 16 and thegas blowing nozzle 17 are simultaneously movable forward and backward.The gas blowing nozzle 17 is urged forward by a spring 19, and slightlyprotrudes forward relative to the heating plates 15 and 16.

When the blank 120 stops at the gas filling position (FIG. 5( a)), theheating plates 15 and 16 and the gas blowing nozzle 17 move forward asshown in FIG. 5( b), and the cylindrical tip of the gas blowing nozzle17 comes into contact with the periphery of the slit 111 formed in thenon-sealed region 106. Meanwhile, on the back surface side, the heatingplate 18 moves forward and supports the back surface side of the blank120 (back surface side of the slit 111), and simultaneously, gas isblown out from the gas blowing nozzle 17. When the gas blowing starts,the gas pressure causes the gas blowing nozzle 17 to slightly movebackward against the urging force as shown in FIG. 7, and a gap isformed between the first side-surface film and the second side-surfacefilm. Then, the gas is blown into the non-sealed region 106 through theslit 111, and thereby the non-sealed region 106 expands. When the urgingforce is F, the gas pressure is P, and the nozzle opening area is S, therelationship between the urging force and the gas pressure is set toF<P×S. In the state where the blank 120 is closely sandwiched betweenthe gas blowing nozzle 17 and the heating plate 18 and the firstside-surface film and the second side-surface film are closely adheredto each other at the entire periphery of the slit 111, gas blowing isnot performed. A gap needs to be formed between the first side-surfacefilm and the second side-surface film at the entirety or part of theperiphery of the slit 111.

Subsequently, as shown in FIG. 5( c), the heating plates 15 and 16further move forward, and the heating plate 15 comes into contact withthe upper end of the opening of the blank 120 while the heating plate 16comes into contact with a position directly beneath the slit in thenon-sealed region 106, whereby the line seal portion 13 and the sealportion 12 are formed, and simultaneously, gas blowing from the gasblowing nozzle 17 stops. Subsequently, as shown in FIG. 6( a), theheating plates 15 and 16, the gas blowing nozzle 17, and the heatingplate 18 move backward. Meanwhile, the blank 120 is rotationally movedto the following sealing position (FIG. 6( b)). In the sealing position,a pair of heating plates 21 and 22 are disposed facing each other acrossthe blank 120. When the blank 120 stops at this position, as shown inFIG. 6( c), the heating plates 21 and 22 move forward and flatly sealsthe opening including the slit 111, whereby a seal portion 14 is formed.After the formation of the seal portion 14, the blank 120 isrotationally moved, and the opening is cooled and sealed at thefollowing cooling position (not shown). Further, the gripper is openedat a release position to release the blank 120. Through theabove-described process steps, the gas is filled in the non-sealedregion 106, whereby the gas injection portion 107 is formed.

(Gas Injected to Gas Injection Portion)

The gas to be injected into the gas injection portion 107 to form thenon-sealed region 106 is not limited. For example, a gas having specificheat at constant volume equal to or larger than 0.67 kJ/kg·deg at 0° C.and 1 atm (101.325 kPa) may be used. When such a gas is used, even ifthe temperature of the contents or the outside air temperature is high,the temperature of the inside of the gas injection portion 107 is notlikely to rise, whereby pressure increase can be suppressed. Thus, it ispossible to reduce the possibility of peeling from near the gasinjection portion 107 to the side edge of the flexible package 100, andleakage of the gas to the outside from a gap between the firstside-surface film 101 and the second side-surface film 102.

(Repelling Force of Gas Injection Portion)

The stability of self-standing of the flexible package 100 and the easeof discharging the contents are increased as the gas injection portion107 is less likely to bend. The gas injection portion 107 is less likelyto bend as the repelling force when the gas injection portion 107 issqueezed is larger. The inventors have discovered that thedifficult-to-bend property of the gas injection portion 107 can befavorably evaluated by measuring the repelling force when the entiretyof the gas injection portion 107 is nipped from the first side-surfacefilm 101 side and the second side-surface film 102 side and is squeezeduntil the width of the nipped portion 107 becomes half the diameter R ofthe gas injection portion 107. FIG. 8( a) shows an enlargedcross-sectional view of the gas injection portion 107 which is notsqueezed, and FIG. 8( b) shows an enlarged cross-sectional view of thesqueezed gas injection portion 107. As shown in FIGS. 8( a) and 8(b),when the entirety of the gas injection portion 107 is nipped betweenflat surfaces of two jigs 112 and squeezed up to the width half thediameter R, the volume reduction rate of the gas injection portion 107can be a constant value that does not depend on the diameter R and thelength. The repelling force applied to the jigs 112 at this time may beregarded as a restoring force of the entirety of the gas injectionportion 107 to restore to the original shape. Therefore, it isconceivable that, by using the above method, the difficult-to-bendproperty of the gas injection portion 107 can be evaluated withoutgreatly depending on the size of the gas injection portion 107.

The repelling force is preferably 4 N or more at 23° C. and 1 atm(101.325 kPa) since the stability of the flexible package 100 in itsself-standing posture is improved. More preferably, the repelling forceis 7 N or more since the shape of the flexible package 100 when thecontents are discharged is not deformed and thereby the ease ofdischarging the contents is improved. If the repelling force is 30 N orless, it is possible to prevent the situation where, at 23° C., the gasinjection portion 107 is broken or the seal portion near the gasinjection portion 107 is peeled and thereby the gas leaks to theoutside. More preferably, the repelling force is 26 N or less since suchleakage of the gas can be prevented even if the temperature of the gasinjection portion 107 is as high as 50° C. Therefore, the repellingforce is, at 23° C. and 1 atm, preferably not smaller than 4 N but notlarger than 30 N, and more preferably, not smaller than 4 N but notlarger than 26 N. By adjusting the repelling force within this range, itis possible to provide a flexible package including a gas injectionportion that has a constant difficult-to-bend property and reduces thepossibility of leakage of the gas. Such adjustment of the repellingforce can be realized by controlling the pressure of the gas blown intothe gas injection portion 107.

(Rigidity of Side-Surface Films)

The flexible package 100 may have the following features. That is, loopstiffness LSv of the first side-surface film 101 and the secondside-surface film 102 in a direction corresponding to the top-bottomdirection of the self-standing flexible package 100 is not smaller than30 mN/25 mm (width) but not larger than 1300 mN/25 mm (width), and loopstiffness LSh of the first side-surface film 101 and the secondside-surface film 102 in a direction corresponding to the left-rightdirection of the self-standing flexible package 100 is not smaller than20 mN/25 mm (width) but not larger than 1200 mN/25 mm (width). The loopstiffness is as follows. That is, as shown in FIG. 9, a loop is formedby using a film cut into a strip shape of a predetermined size, and theloop is pressed by a predetermined amount in the diameter direction, andthen the repelling force of the loop is measured. The loop stiffness isthe measured repelling force, and is an index indicating the rigidity ofthe film. The larger the value of the loop stiffness is, the higher therigidity of the film is. How to measure the loop stiffness will bedescribed later.

If the values of loop stiffnesses LSv and LSh go below the above range,when the flexible package 100 is made to stand by itself, the shape ofthe flexible package 100 cannot be retained by only the rigidity of thegas injection portion 107, resulting in undesirable situations such asbending of the upper portion of the flexible package 100, and falling ofthe flexible package 100. On the other hand, if the values of the loopstiffnesses LSv and LSh exceed the above range, the toughness of thefirst side-surface film 101 and the second side-surface film 102 isexcessively increased, which makes the package forming processingdifficult.

Within the above range, more preferably, the value of the loop stiffnessLSh is not smaller than 80 mN/25 mm (width) but not larger than 550mN/25 mm (width), and the value of the loop stiffness LSv is not smallerthan 80 mN/25 mm (width) but not larger than 480 mN/25 mm (width). Inthis case, the self-standing property of the flexible package 100 can bestably maintained, and the package forming processing is facilitated.

Within the above range, when the value of the loop stiffness LSh is notsmaller than 20 mN/25 mm (width) but not larger than 80 mN/25 mm (width)and the value of the loop stiffness LSv is not smaller than 30 mN/25 mm(width) but not larger than 80 mN/25 mm (width), a thinner and cheaperfilm can be used as the first side-surface film 101 and the secondside-surface film 102 as compared to the case where a flexible packagehaving no gas injection portion 107 is configured. Therefore, inaddition to the excellent self-standing property of the flexible package100 and the easiness of the package forming processing, the productioncost of the flexible package 100 can be reduced.

The material of the first side-surface film 101 and the secondside-surface film 102 is not particularly limited. For example, amultilayer film including a sealant layer as an innermost layer may beused. The first side-surface film 101 and the second side-surface film102 may include a resin layer, a metal foil layer, a vapor depositionlayer of metal or inorganic oxide, or the like, depending on the purposeof the flexible package 100. The effect of improving the self-standingproperty of the flexible package 100 and the easiness of processingthereof can be achieved by setting the values of the loop stiffnessesLSv and LSh within the above range, without depending on the layerstructure of the first side-surface film 101 and the second side-surfacefilm 102.

Generally, a flow direction (MD: Machine Direction) of the firstside-surface film 101 and the second side-surface film 102 correspondsto the left-right direction of the self-standing flexible package 100,and a direction (TD: Transverse Direction) perpendicular to the flowdirection of the first side-surface film 101 and the second side-surfacefilm 102 corresponds to the top-bottom direction of the self-standingflexible package 100. Thereby, a long film can be used without waste,and the package forming processing can be performed at a high speed.However, even when the MD of the first side-surface film 101 and thesecond side-surface film 102 does not correspond to the left-rightdirection of the self-standing flexible package and the TD of the firstside-surface film 101 and the second side-surface film 102 does notcorrespond to the top-bottom direction of the self-standing flexiblepackage, it is possible to achieve both improvement of the self-standingproperty of the flexible package 100 and the easiness of the packageforming processing, as long as the values of the loop stiffness LSv andthe loop stiffness LSh are within the above ranges.

As described above, by combining the gas injection portion 107 providedin the side edge portion 108 of the flexible package 100 with theoptimized rigidity (loop stiffness) of the first side-surface film 101and the second side-surface film 102, the first side-surface film 101and the second side-surface film 102 are less likely to bend at the gasinjection portion 107 and its vicinity. Therefore, when the flexiblepackage 100 is made to stand by itself, the overall shape of theflexible package 100 is also less likely to deform, and thus theself-standing property of the flexible package 100 is easily maintained.Further, since the rigidity of the first side-surface film 101 and thesecond side-surface film 102 is appropriate, the forming processing ofthe flexible package 100 is facilitated.

(Gas Barrier Property)

The flexible package 100 may have the following features. That is, theamount of the gas permeating the non-sealed region 106 may be controlledby giving gas barrier property to at least the non-sealed region 106.Specifically, in the flexible package 100 according to the presentembodiment, at 20° C. and 60% RH, oxygen permeability of the non-sealedregion 106 is not lower than 0 cc/(m²·day·atm) but not higher than 30cc/(m²·day·atm) [not lower than 0 cm³/(m²·day·MPa) but not higher than296.08 cm³/(m²·day·MPa)]. By setting the oxygen permeability of thenon-sealed region 106 to be not higher than 30 cc/(m²·day·atm) at 20° C.and 60% RH, reduction in the inner pressure of the gas injection portion107 formed by injecting the gas in the non-sealed region 106 issuppressed. Therefore, the shape retaining property of the flexiblepackage 100 due to the gas injection portion 107 and the function of thegas injection portion 107 as a handle can be maintained for a longperiod of time. In order to further suppress reduction in the innerpressure of the gas injection portion 107, the oxygen permeability ofthe non-sealed region 106 is, at 20° C. and 60% RH, preferably not lowerthan 0 cc/(m²·day·atm) but not higher than 5 cc/(m²·day·atm) [not lowerthan 0 cm³/(m²·day·MPa) but not higher than 49.34 cm³/(m²·day·MPa)], andmore preferably, not lower than 0 cc/(m²·day·atm) but not higher than 1cc/(m²·day·atm) [not lower than 0 cm³/(m²·day·MPa) but not higher than9.86 cm³/(m²·day·MPa)].

As described above, any type of gas may be adopted as the gas injectedinto the non-sealed region 106. However, since oxygen permeability isusually adopted as an index indicating the gas barrier property of afilm, oxygen permeability may be adopted as a value representing the gasbarrier property of the non-sealed region 106. By using a film whoseoxygen permeability value is within the above range, reduction in theinner pressure of the gas injection portion 107 can be suppressedregardless of the type of the gas to be sealed, whereby the shaperetaining property of the flexible package 100 and the function of theflexible package 100 as a handle can be maintained.

As a method of giving gas barrier property to the non-sealed region 106,a multilayer film including a gas barrier layer made of a materialhaving gas barrier property may be used as the first side-surface film101 and the second side-surface film 102. Alternatively, a gas barrierlayer may be partially provided in a region where the non-sealed region106 is provided. Examples of the gas barrier layer include: a metal foilsuch as aluminum, a metal deposition layer such as aluminum, aninorganic oxide deposition layer, a resin film composed of a resinhaving high gas barrier property, such as nylon, a gas barrier filmobtained by depositing metal or inorganic oxide on the surface of aresin film, and a barrier coat layer formed by coating of a barriercoating agent. Examples of the inorganic oxide deposition layer includedeposition films of silicon oxide, aluminum oxide, magnesium oxide,titanium oxide, tin oxide, and the like.

As a method of partially giving gas barrier property to the non-sealedregion 106, metal or inorganic oxide may be partially deposited on aportion, including a region to be the non-sealed region 106, of thefirst side-surface film 101 and the second side-surface film 102.Alternatively, the portion including the region to be the non-sealedregion 106 may be partially coated with a barrier coating agent.Alternatively, a film including a gas barrier layer may be partiallybonded to the portion including the region to be the non-sealed region106. When gas barrier property is not necessary for the contents filledin the flexible package 100, the method of coating the barrier coatingagent is preferable because, in this method, gas barrier property can bepartially given easily and inexpensively.

As the above-described gas barrier film, a film having the followingstructure may be used.

FIG. 10 is a schematic cross-sectional view showing an example of alayer structure of the gas barrier film.

A gas barrier film 130 shown in FIG. 10 is configured by laminating abase material 131, a foundation layer 132, a vapor-deposited layer 133,and a gas barrier coating layer 134 in this order.

As the base material 131, a stretched nylon film, a stretched polyesterfilm, a stretched polypropylene film, or the like may be used.

The foundation layer 132 is a layer provided for enhancing adhesion ofthe vapor-deposited layer 133. An example of a method for forming thefoundation layer 132 is as follows. First, in a dilute solvent such asethyl acetate, 1 part by weight of y-isocyanatopropyltriethoxysilane and5 parts by weight of acrylic polyol are mixed, and stirred. Next, inthis mixed solution, as isocyanate compounds, XDI (xylylenediisocyanate) and IPDI (isophorone diisocyanate) are further mixed. Theamount of each isocyanate compound is controlled so that the number ofmoles of isocyanate group (NCO group) of the isocyanate compound isequal to the number of moles of hydrogen group (OH group) of acrylicpolyol. The solution in which the isocyanate compounds are added isdiluted so that the total solid content is 2% by weight, and the dilutedsolution is applied to the surface of the base material 131 by gravurecoating, thereby forming the foundation layer 132.

The vapor-deposited layer 133 is a gas barrier layer formed by vapordeposition of an inorganic oxide such as silicon oxide, aluminum oxide,magnesium oxide, titanium oxide, tin oxide or the like.

The gas barrier coating layer 134 is a gas barrier layer formed bycoating of a barrier coating agent. An example of a method of formingthe gas barrier coating layer 134 is as follows. First, 89.6 g of 0.1Nhydrochloric acid is added to 10.4 g of tetraethoxysilane (Si(OC₂H₅)₄),and the resultant solution is stirred for 30 minutes to be hydrolyzed.Next, the hydrolyzed solution having a solid content of 3.0% by weight(a value based on the weight of SiO₂), which is obtained by thehydrolysis, is mixed with water-isopropyl alcohol solution(water:isopropyl alcohol (weight ratio)=90:10) containing 3.0% by weightof polyvinyl alcohol, at a ratio of 60:40, thereby preparing a barriercoating agent. The prepared barrier coating agent is coated over thevapor-deposited layer 133, thereby forming the gas barrier coating layer134.

As described above, in the flexible package 100 having the gas injectionportion 107, the oxygen permeability of the non-sealed region 106 is setwithin the above-described range, whereby reduction in the innerpressure of the gas injection portion 107 can be suppressed. As aresult, the shape retaining property of the flexible package 100 and thefunction of the gas injection portion 107 as a handle can be maintainedfor a long period of time.

(Seal Strength)

The flexible package 100 may have the following features. That is, theseal strength of the side edge portion 108 in which the non-sealedregion 106 is formed or the gas injection portion 107 is further formedmay be set to 30 N/15 mm or more. Thereby, the seal is not peeled by thegas pressure when the gas injection portion 107 is formed or by increasein the pressure when the temperature inside the formed gas injectionportion 107 is high, and thus the possibility of gas leakage or flow ofthe contents into the gas injection portion is reduced. The side edgeportion 108 is a portion in which at least the first side-surface film101 and the second side-surface film 102 are sealed with each other, andmay include or may not include a portion in which the first side-surfacefilm 101 and the bottom film 103 are sealed with each other or a portionin which the second side-surface film 102 and the bottom film 103 aresealed with each other. The seal strength is preferably 50 N/15 mm orhigher since the strength of the flexible package 100 can be ensuredmore sufficiently.

If the seal strength is excessively high, processing costs for sealing,such as the temperature, time, and pressure, are high. In addition, atthe boundary between the non-sealed region 106 and the sealed region,the first side-surface film 101 and the second side-surface film 102 maybe spuriously adhered to each other, which may deform the shape of thenon-sealed region 106 or the gas injection portion 107. The sealstrength is more preferably 100 N/15 mm or lower. In this case, thecosts of the sealing process are reduced. in addition, since spuriousadhesion is suppressed, the non-sealed region 106 or the gas injectionportion 107 can be formed without shape deformation.

(Shape)

The flexible package 100 or the blank 120 may have any of the followingfeatures.

<Shape of Blank: First Feature>

As shown in FIG. 3, the distance a from the upper end of the non-sealedregion 106 to the upper end of the blank 120 is 30% or less of theheight H of the blank 120. When a slit such as the slit 111 or a hole isformed at the upper end of the non-sealed region 106, the distance a′from the lower end of the slit or hole to the upper end of the blank 120is also 30% or less of the height H of the blank 120. When a pluralityof non-sealed regions 106 are provided, at least one of the non-sealedregions 106 may satisfy this condition.

<Shape of Blank: Second Feature>

The length W (hereinafter referred to as “width W”) in the left-rightdirection along the first side-surface film 101 or the secondside-surface film 102 at the lower end of the blank 120, and thedistance B from the lower end of the blank 120 to the fold line of thebottom film 103, i.e., the insertion length B of the bottom film 103,satisfy the relationship of 0.15≦(B/W)<0.5.

<Shape of Blank: Third Feature>

The lower end of the discharge part 104 of the blank 120 is positionedbelow the upper end of the non-sealed region 106. When a slit such asthe slit 111 or a hole is formed at the upper end of the non-sealedregion 106, the lower end of the discharge part 104 is positioned belowthe lower end of the slit or the hole.

The flexible package 100 in the state where contents are filled in theblank 120 having the above features has the following features.

<Shape of Flexible Package: Fourth Feature>

As shown in FIG. 1, the distance A from the upper end of the gasinjection portion 107 to the upper end of the flexible package 100 is30% or less of the height H of the flexible package 100. The flexiblepackage 100 has this fourth feature when the blank 120 has the abovefirst feature and no slit 111 is formed at the upper end of thenon-sealed region 106. When the slit 111 is formed at the upper end ofthe non-sealed region 106, the flexible package 100 is allowed to havethe fourth feature by when an appropriate range near the slit 111 issealed. When a wider range including a portion lower than the lower endof the slit 111 is sealed in order to prevent, more reliably, the gasfrom escaping through the slit 111, the slit 111 may be provided at ahigher position.

<Shape of Flexible Package: Fifth Feature>

The contents are injected up to a height that does not exceed the upperend of the gas injection portion 107. That is, the distance C from theupper end of the contents to the upper end of the flexible package 100and the distance A from the upper end of the gas injection portion 107to the upper end of the flexible package 100 satisfy the relationship ofC≧A. The flexible package 100 generally has this fifth feature when theblank 120 has the above third feature, because, generally, the contentsare injected into the storage part 105 to a height that does not reachthe lower end of the opening of the discharge part 104 so as to preventthe contents from accidentally spilling out from the discharge part 104.Even when the blank 120 does not have the third feature, the flexiblepackage 100 is allowed to have the fifth feature by controlling theamount of the contents to be injected with reference to the height ofthe upper end of the gas injection portion 107 instead of the height ofthe discharge part 104. Therefore, the blank 120 may not have the thirdfeature.

When the blank 120 has the second feature, the flexible package 100 alsohas the second feature, and the width W and the insertion length Bsatisfy the relationship of 0.15≦(B/W)<0.5. Thereby, in the flexiblepackage 100, the bottom sides of the first side-surface film 101 and thesecond side-surface film sufficiently expand, and the bottom film 103sufficiently stretches. Thus, the flexible package 100 is easily made tostand by itself, and the storage part can be favorably formed. Inaddition, when the flexible package 100 has the fourth and fifthfeatures, the gas injection portion 107 may be provided up to a positionhigher than the contents to make the shape of the flexible package 100difficult to deform. Thus, the flexible package 100 can easily retainthe self-standing posture, and the contents can be easily injected.Further, the first feature and the third feature make it easy to obtainthe fourth feature and the fifth feature, respectively.

FIG. 11 shows a plan view of a blank 200 according to a modification ofthe blank having the above features. In the blank 200, the dischargepart 104 is formed not by attaching a spout member but by molding thefirst side-surface film 101 and the second side-surface film 102 in anozzle shape. Thus, the structure of the discharge part 104 of the blankor the flexible package is not particularly limited. For example, thedischarge part 104 may be a slit that leads to an opening. The blank andthe flexible package need not have all the above-mentioned features. Forexample, the blank may have only the second feature, and the flexiblepackage may have only the fourth and fifth features.

(Cut Guide Portion)

The flexible package 100 may have the following feature. That is, in theside edge portion 108, a cross-shaped slit 113 may be formed at aposition near the gas injection portion 107, as a cut guide portion thatguides cutting of the first side-surface film 101 and the secondside-surface film 102 from the position to the gas injection portion107. As shown in FIGS. 12( a), 12(b) and 13, the cross-shaped slit 113is provided near the upper end of the gas injection portion 107, and iscomposed of two slit portions that penetrate the first side-surface film101 and the second side-surface film 102 and extend in the left-rightdirection and the top-bottom direction, respectively.

The slit 113 is used for discharging the gas from the gas injectionportion 107 when the flexible package 100 from which the contents havebeen taken out is rolled up. The procedure to discharge the gas will bedescribed with reference to FIGS. 12( a) and 12(b). As shown in FIG. 12(a), the flexible package 100 is bent along the slit portion, of the slit113, extending in the left-right direction. Thereby, the slit portion,of the slit 113, extending in the top-bottom direction is exposed on thefold line. Next, as shown in FIG. 12( b), the first side-surface film101 and the second side-surface film 102 are torn from the slit portion,of the slit 113, extending in the top-bottom direction to extend theslit portion to the gas injection portion 107, thereby opening the gasinjection portion 107. Thus, the gas in the gas injection portion 107 isdischarged, and the flexible package 100 can be easily rolled up so asnot to be bulky when it is discarded. In addition, since the flexiblepackage 100 has to be bent before it is torn, the flexible package 100is less likely to be accidentally torn from the slit 113 when it isnormally handled.

The slit 113 is preferably provided at a position within 15 mm upwardfrom the upper end of the gas injection portion 107 so that the extendedslit easily reaches the gas injection portion 107. Further, of the slit113, the slit portion in the left-right direction preferably has alength of 1 mm or more so as to facilitate bending of the flexiblepackage 100, and the slit portion in the top-bottom direction preferablyhas a length of 1 mm or more so that the slit portion easily triggerstearing.

In at least one of the first side-surface film 101 and the secondside-surface film 102, an indication that indicates the presence,position, or the like of the slit 113 is provided on or near the slit113. In the example shown in FIG. 13, the position of the slit 113 as adegassing point is indicated by a circle and characters. In addition, adotted line is provided along the slit portion, of the slit 113, in theleft-right direction, which induces the user to bend the flexiblepackage 100 along the dotted line. The indication is not limited to theabove example, and may be implemented by various colors, figures,shapes, symbols, and the like. In addition to the indication, the aboveprocedure of degassing may be described in detail at any position on theflexible package 100.

The slit 113 may be formed such that, in the process of producing theflexible package 100, the slit 111 and its vicinity are not sealed,i.e., are left non-fused.

FIG. 14 shows a plan view of a flexible package 300 having another cutguide portion. The flexible package 300 is different from the flexiblepackage 100 in the cut guide portion. In the flexible package 300, thecut guide portion is a slit 311 which is formed in a portion near thegas injection portion 107 on the storage part 105 side so as topenetrate the first side-surface film 101 and the second side-surfacefilm 102. For example, the slit 311 is a curved line projecting towardthe storage part 105 side. Another example of a slit is shown in FIG.15( a). In the example shown in FIG. 15( a), a slit 312 has a shapecomposed of a straight line of a predetermined length extending in thetop-bottom direction, and arcs extending from both ends of the straightline toward the gas injection portion 107. Instead of the slits 311 and312, as shown in FIG. 15( b), a hole 313 may be formed by cutting anoval shape out of the first side-surface film 101 and the secondside-surface film 102.

With reference to FIGS. 16( a)-16(c), the procedure to discharge the gasfrom the gas injection portion 107 of the flexible package 300 shown inFIG. 14 will be described. As shown in FIG. 16( a), first, a userinserts a finger in the slit 311, and bends the first side-surface film101 and the second side-surface film 102. Next, as shown in FIG. 16( b),the user tears the first side-surface film 101 and the secondside-surface film 102 from the slit 311 and extends the slit 311 to thegas injection portion 107, thereby opening the gas injection portion107. The same applies to the case of providing the slit 312 shown inFIG. 15( a). Thereby, the gas in the gas injection portion 107 isdischarged, and the flexible package 100 can be easily rolled up so asnot to be bulky when it is discarded. In addition, since the firstside-surface film 101 and the second side-surface film 102 need to bebent before they are torn, the flexible package 300 is less likely to beaccidentally torn from the slit 311 when it is normally handled.Further, as shown in FIG. 16( c), the user may further extend the slit311 to the outer edge of the flexible package 100, and tear off aportion of the flexible package 100 including a portion of the gasinjection portion 107.

Also when the hole 313 is formed in the flexible package 300, the userinserts a finger in the hole 313, and tears the first side-surface film101 and the second side-surface film 102 from the hole 313 to reach thegas injection portion 107, whereby the gas in the gas injection portion107 can be discharged.

The slit 311 or the slit 312 is preferably formed to be close to thecenter portion of the gas injection portion 107 excluding the both endsthereof in the top-bottom direction, in order to enable more reliabletearing of the gas injection portion 107. In at least one of the firstside-surface film 101 and the second side-surface film 102, anindication that indicates the presence, position, or the like of any ofthe slit 311, the slit 312, and the hole 313 may be performed on theslit (hole) or its vicinity.

FIG. 17 shows a plan view of a flexible package 400 having another cutguide portion. The flexible package 400 is different from the flexiblepackage 100 in the non-sealed region and the cut guide portion. In theflexible package 400, a non-sealed region 406, in a predetermined regionincluding a lower end thereof, has a width of 3 mm or more in theleft-right direction, and is 5 mm or more apart from the outer edge ofthe first side-surface film 101 and the second side-surface film 102. Inaddition, in the flexible package 400, a cut guide portion is aneasy-to-cut portion 411 formed by arranging a plurality of fine flaws onthe surface within a predetermined range, extending from the outer edgeof the first side-surface film 101 and the second side-surface film 102to the gas injection portion 407 formed in the predetermined region.

As shown in FIG. 18, when the first side-surface film 101 and the secondside-surface film 102 are torn along the easy-to-cut portion 411 and theeasy-to-cut portion 411 is extended to the gas injection portion 407,the gas injection portion 407 is opened, and thereby the gas isdischarged from the gas injection portion 407. Thus, the flexiblepackage 400 can be easily rolled up so as not to be bulky when it isdiscarded.

Since a portion of the non-sealed region 406 near the easy-to-cutportion 411 is 5 mm or more apart from the outer edge, the expanded gasinjection portion 407 in this portion is apart from the outer edge.Therefore, a scratch work to form the flaws in the easy-to-cut portion411 is easy to perform. In addition, the easy-to-cut portion 411 is easyto pinch, which makes tearing easy. In addition, since the portion ofthe non-sealed region 406 near the easy-to-cut portion 411 has a widthof 3 mm or more in the left-right direction, spurious adhesion over theentire width is prevented, whereby the gas injection portion 407 can beformed with reliability. As shown in FIG. 17, the width of thenon-sealed region 406 in the left-right direction, in a region otherthan the portion near the easy-to-cut portion 411, is preferably largerthan the width thereof near the easy-to-cut portion 411 to make the gasinjection portion 407 expand more.

Alternatively, as shown in FIG. 19, the non-sealed region 406 may have auniform width in the left-right direction, and an easy-to-cut portion412 may be arranged in a curved region extending from the outer edgelower than the lower end of the gas injection portion 407 to the lowerend of the gas injection portion 407.

The features of the flexible package according to the present inventionhave been described above. The flexible package may have all or part ofthe above-described features. It is apparent that a useful embodiment isachieved by any combination of the above-described features. Inaddition, the present invention is applicable not only to aself-standing flexible package having a bottom film but also to aflexible package that has no bottom film and is formed by joining afirst side-surface film and a second side-surface film together. Also inthis case, it is possible to improve portability of the flexiblepackage, ease of discharging contents, and toughness against bending.

EXAMPLES

Hereinafter, examples, comparative examples, and evaluation results ofthe present invention will be described.

(Gas to be Injected into Gas Injection Portion)

Comparative Example 1-1 and Examples 1-2 to 1-5 of flexible packages100, in which gas injection portions 107 were formed by injection ofgases at 20° C. that were generated by mixing carbon dioxide andnitrogen at different ratios so as to have different specific heats atconstant volume, were left for 30 minutes at 80° C. and observed. Theobservation result is shown in the following Table 1.

TABLE 1 Specific heat at constant volume Observation (0° C., 1 atm)result Evaluation Com. Exam. 1-1 0.155 kcal/kg · deg Peeling of seal −0.648 kJ/kg · deg Gas leakage Exam. 1-2 0.160 kcal/kg · deg Peeling ofseal + 0.669 kJ/kg · deg No gas leakage 1-3 0.165 kcal/kg · deg Peelingof seal + 0.690 kJ/kg · deg No gas leakage 1-4 0.170 kcal/kg · deg Nopeeling of seal ++ 0.711 kJ/kg · deg No gas leakage 1-5 0.175 kcal/kg ·deg No peeling of seal ++ 0.732 kJ/kg · deg No gas leakage

In Table 1, “++” indicates that the evaluation result was good, “+”indicates that the evaluation result was inferior to “++” but was withinan allowable range, and “−” indicates that the evaluation result was notgood. In Table 1, unit conversion of the specific heat at constantvolume was performed with 1 cal=4.18 J.

In Comparative Example 1-1, peeling of the sealed portion near the gasinjection portion 107 occurred. The peeling advanced up to the side edgeof the flexible package 100, and the gas leaked to the outside from agap between the first side-surface film 101 and the second side-surfacefilm 102. In Examples 1-2 and 1-3, although peeling of the sealedportion occurred, the peeling did not advance up to the side edge of theflexible package 100, and no gas leakage was observed. In Examples 1-4and 1-5, no peeling of the sealed portion occurred, and no gas leakagewas observed.

From the above result, it was confirmed that no gas leakage occurs whenthe specific heat at constant volume of the gas inside the gas injectionportion 107 is not lower than 0.160 kcal/kg·deg, i.e., not lower thanabout 0.67 kJ/kg·deg. In addition, it was confirmed that no peeling ofthe sealed portion occurs even under the high temperature when thespecific heat at constant volume is not lower than 0.170 kcal/kg·deg,i.e., not lower than about 0.71 kJ/kg·deg.

(Repelling Force of Gas Injection Portion)

Comparative Examples 2-1 and 2-2 and Examples 2-3 to 2-15 of flexiblepackages 100 were produced in which the diameter R of the gas injectionportion 107 was 6 mm and the repelling force of the gas injectionportion was varied, and were preserved for one month at 1 atm and atdifferent temperatures of 23° C. (room temperature), 40° C., and 50° C.Then, the respective Comparative Examples and Examples were evaluatedfor stability of self-standing and ease of discharging contents. Each ofComparative Examples and Examples had a height of 282.5 mm, a width of178 mm, and a capacity of 900 ml. The gas injection portion 107 wasformed by injecting a gas into the non-sealed region 106 having a widthof 10 mm, and had a cylindrical shape having a diameter R of 6 mm. Theseal strength near the gas injection portion 107 was 110 N/15 mm. Eachof Comparative Examples and Example was formed by using a laminateincluding polyethylene terephthalate, aluminum, nylon, and polyethylene.The evaluation result is shown in the following Table 2.

TABLE 2 Com. Exam. Exam. 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-112-12 2-13 2-14 2-15 Repelling 1 3 5 7 10 12 14 16 18 20 22 25 26 28 30force (N) 23° C. − − + ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ 40° C. − − +++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ − 50° C. − − + ++ ++ ++ ++ ++ ++ ++ ++++ ++ − −

In Table 2, “++” indicates that the evaluation result was good. That is,since the gas injection portion 107 was less likely to bend, theflexible package was allowed to stably stand by itself. In addition,when the contents were discharged, the gas injection portion 107 waseasy to hold, and it was easy to stabilize the direction of thedischarge part 104, and therefore, it was easy to discharge thecontents. Further, “+” indicates that the evaluation result was inferiorto “++”, but was within an allowable range. That is, although ease ofdischarging the contents could not be achieved, the flexible package wasallowed to stably stand by itself. Further, “−” indicates that theevaluation result was not good. That is, the gas injection portion 107was likely to bend, or gas leakage occurred, which did not contribute tostability of self-standing and ease of discharging the contents. Thus,the effect of providing the gas injection portion 107 could not beconfirmed.

At any preservation temperature, Examples 2-4 to 2-13 (repelling forcewas not smaller than 7 N but not larger than 26 N) provided the goodresult, and Example 2-3 provided the result within the allowable range.Example 2-14 (repelling force was 28 N) provided the good result when itwas preserved at 23° C. and 40° C. However, under preservation at 50°C., peeling of seal occurred extending from the gas injection portion107 to the side edge of the flexible package 100, and gas leakageoccurred. Example 2-15 (repelling force was 30 N) provided the goodresult when it was preserved at 23° C. However, under preservation at40° C. and 50° C., peeling of seal and gas leakage similarly occurred.In Comparative Examples 2-1 and 2-2 (repelling force was 3 N or less),the gas injection portion 107 was likely to bend, and stableself-standing and ease of discharging the contents were not achieved.

Therefore, it was confirmed that, when the flexible package 100 ispreserved at a room temperature of about 23° C., the repelling force ispreferably not smaller than 4 N but not larger than 30 N (Examples), andmore preferably, not smaller than 7 N but not larger than 30 N.

Further, it was confirmed that, when there is a possibility that thetemperature of the gas injection portion 107 is 50° C. or more becausehigh-temperature contents are injected or the package is left inhigh-temperature environment, the repelling force is preferably notsmaller than 4 N but not larger than 26 N, and more preferably, notsmaller than 7 N but not larger than 26 N.

In each of Comparative Examples 2-1 and 2-2 and Examples 2-3 to 2-15,the diameter R of the gas injection portion 107 was varied to 3 mm, 20mm, and 50 mm, and thus obtained samples were preserved for one month at1 atm and 50° C. Then, the respective Comparative Examples and Exampleswere evaluated for stability of self-standing and ease of dischargingthe contents. The evaluation result is shown in the following Table 3.In Table 3, the result obtained when the diameter R of the gas injectionportion 107 is 6 mm is again shown for comparison.

TABLE 3 Com. Exam. Exam. 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-112-12 2-13 2-14 2-15 Repelling 1 3 5 7 10 12 14 16 18 20 22 25 26 28 30force (N) Diameter − − + ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ 3 mmDiameter − − + ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ − − 6 mm Diameter − − ++ ++++ ++ ++ ++ ++ ++ ++ ++ ++ − − 20 mm Diameter − − ++ ++ ++ ++ ++ ++ ++++ ++ ++ ++ − − 50 mm

In Table 3, the meanings of “++”, “+” and “−” are similar to those inTable 2. With any diameter, the result was good when the repelling forcewas not smaller than 7 N but not larger than 26 N. When the repellingforce was 28 N and 30 N, the result was good when the diameter R was 3mm, but the result was not good because of gas leakage when the diameterwas 6 mm or more. When the repelling force was 5 N, the result waswithin the allowable range when the diameter R was 3 mm and 6 mm, andthe result was good when the diameter R was 20 mm and 50 mm. When therepelling force was 1 N and 3 N, the result was not good in both cases.

Further, it was confirmed that, when there is a possibility that thetemperature of the gas injection portion 107 is 50° C. or more becausehigh-temperature contents are injected or the package is left inhigh-temperature environment, the diameter R of the gas injectionportion 107 is preferably set in a range from 3 mm to 50 mm, and therepelling force is preferably not smaller than 4 N but not larger than26 N, and more preferably, not smaller than 7 N but not larger than 26N.

(Rigidity of Side-Surface Films)

Flexible packages each having a spout shown in FIG. 1 were produced asExamples 3-2 to 3-8 and Comparative Examples 3-1 and 3-9. Each flexiblepackage had a width (corresponding to W in FIG. 3) of 180 mm, and aheight (corresponding to H in FIG. 3) of 280 mm. In each of Examples andComparative Examples, a film having loop stiffness shown in thefollowing Table 4 was used for the first side-surface film, the secondside-surface film, and the bottom film.

FIG. 9 is a schematic diagram illustrating a loop stiffness measuringmethod. As a sample for loop stiffness measurement, a strip-shaped filmhaving a width of 25 mm and a length of 120 mm was cut out from each ofthe same films as used for production of the flexible packages accordingto Examples and Comparative Examples. The strip-shaped film was cut outso that its longitudinal direction corresponded to the direction of themeasurement target. The strip-shaped film was set on a loop stiffnesstester manufactured by Toyo Seiki Kogyo Co., Ltd., and a loop wasformed. A contact plate of the tester was pressed against the formedloop to squeeze the loop, and the repelling force of the loop wasmeasured. The squeezing distance was 20 mm, and the compression rate was3.5 mm/s. The value (mN) of the measured repelling force was regarded asthe loop stiffness.

The evaluation criteria for self-standing property and formability areas follows:

(1) Self-Standing Property

++: The self-standing posture was maintained without hanging and bendingof the upper part of the flexible package.

+: The self-standing posture was maintained although the upper part ofthe flexible package was slightly deformed.

−: The self-standing posture was not maintained because of hanging andbending of the upper part of the flexible package.

(2) Formability

++: The package forming processing was performed without any problem.

+: The easiness of the package forming processing was degraded due tothe high stiffness of the film, but was not degraded to an extent thatmakes the package forming processing difficult.

−: The package forming processing was difficult due to the excessivelyhigh stiffness of the film.

Table 4 shows the values of the loop stiffnesses of the films used forExamples 3-2 to 3-8 and Comparative Examples 3-1 and 3-9, and theevaluation results of self-standing properties and formabilities of theflexible packages according to Examples 3-2 to 3-8 and ComparativeExamples 3-1 and 3-9.

TABLE 4 Loop stiffness (mN) LSh LSv Self- (left-right (up-down standingdirection) direction) property Formability Com. 3-1 0.4 0.1 − ++ Exam.Exam. 3-2 20 30 + ++ 3-3 80 80 ++ ++ 3-4 100 120 ++ ++ 3-5 145 145 ++ ++3-6 250 200 ++ ++ 3-7 550 480 ++ ++ 3-8 1200 1300 ++ + Com. 3-9 20002000 ++ − Exam.

As shown in Table 4, it was confirmed that, in the flexible packages ofExamples 3-2 to 3-8 which were each produced by using a film whose loopstiffness LSv in the top-bottom direction when the flexible package wasself-standing was not smaller than 30 mN but not larger than 1300 mN andwhose loop stiffness LSh in the left-right direction when the flexiblepackage was self-standing was not smaller than 20 mN but not larger than1200 mN, both the self-standing property and the formability wereexcellent. Further, it was confirmed that, in the flexible packages ofExamples 3-3 to 3-7 which were each produced by using a film whose loopstiffness LSv was not smaller than 80 mN but not larger than 480 mN andwhose loop stiffness LSh in the left-right direction when the flexiblepackage was self-standing was not smaller than 80 mN but not larger than550 mN, both the self-standing property and the formability weresuperior to those of Examples 3-2 to 3-8.

In contrast, it was confirmed that the flexible package according toComparative Example 3-1 was insufficient in the self-standing property,and the flexible package according to Comparative Example 3-9 wasinferior in formability.

(Gas Barrier Property)

Flexible packages each having a spout shown in FIG. 1 were produced asExamples 4-1 to 4-4 and Comparative Example 4-5. The width(corresponding to W in FIG. 3) of each flexible package was 180 mm, andthe height (corresponding to H in FIG. 3) thereof was 280 mm. InExamples 4-1 to 4-4 and Comparative Example 4-5, layer structures offilms used for the first side-surface film, the second side-surfacefilm, and the bottom film are as follows. In each layer structure, anumerical value in parenthesis represents the thickness of each layer.

Example 4-1

A film obtained by laminating, in order from the side to be an outersurface, polyethylene terephthalate (12 μm)/aluminum foil (9 μm)/nylon(15 μm)/LLDPE; Linear Low Density Polyethylene (100 μm) was used.

Example 4-2

A film obtained by laminating, in order from the side to be an outersurface, a transparent deposition gas barrier film (12 μm)/nylon (15μm)/CPP; unstretched polypropylene (70 μm) was used. As the transparentdeposition gas barrier film of Example 4-2, a polyethylene terephthalatefilm having, on one surface thereof, a vapor-deposited inorganic oxide(aluminum oxide) film was used. The film was structure so that thevapor-deposited inorganic oxide film was positioned on the nylon side.

Example 4-3

A film obtained by laminating, in order from the side to be an outersurface, nylon (15 μm)/aluminum deposition gas barrier film (12μm)/LLDPE; Linear Low Density Polyethylene (100 μm) was used. As thealuminum deposition gas barrier film of Example 4-3, a polyethyleneterephthalate film having, on one surface thereof, a vapor-depositedaluminum film was used. The film was structure so that thevapor-deposited aluminum film was positioned on the nylon side.

Example 4-4

a film obtained by laminating, in order from the side to be the outersurface, polyethylene terephthalate (12 μm)/nylon (15 μm)/LLDPE; LinearLow Density Polyethylene (100 μm) was used.

Comparative Example 4-5

a film obtained by laminating, in order from the side to be an outersurface, polyethylene terephthalate (12 μm)/LLDPE; Linear Low DensityPolyethylene (120 μm) was used.

The flexible packages according to Examples 4-1 to 4-4 and ComparativeExample 4-5 were formed using the above-described films so that thenon-sealed region 106 was filled with air and hermetically sealed, andwere preserved under the conditions shown in the following Table 5.

After the preservation period has passed, the state of each gasinjection portion was evaluated for any of “++”, “+”, and “−”, accordingto the following evaluation criteria.

++: No or almost no discharge of air from the gas injection portion wasobserved. As compared to the state immediately after air injection, theshape retaining property of the flexible package and the ease of holdingas a handle were not changed.

+: Although some air was discharged from the gas injection portion, theshape retaining property of the flexible package and the ease of holdingas a handle were sufficiently maintained as compared to the stateimmediately after air injection.

−: Discharge of air from the gas injection portion was significant, andthe gas injection portion was bent. Thus, the shape retaining propertyand the function as a handle were deteriorated.

Table 5 shows oxygen permeabilities of the non-sealed regions of theflexible packages according to Examples 4-1 to 4-4 and ComparativeExample 4-5, and evaluation results under different preservationconditions.

TABLE 5 Oxygen Preservation condition permeability cc/ 20° C., 40° C.,60° C., (m² · day · atm) 1 year 6 months 1 month Exam. 4-1 0 ++ ++ ++4-2 0.5 ++ ++ ++ 4-3 1 ++ ++ ++ 4-4 30 + + + Com. Exam. 4-5 100 − − −

In the flexible package according to Comparative Example 4-5, dischargeof air from the gas injection portion was significant, and the gasinjection portion was bent and the upper part of the flexible packagehung down due to the weight of the contents, and thus the shape of theflexible package was not maintained. In addition, since the innerpressure of the gas injection portion was greatly reduced, the gasinjection portion was bent when the user held the gas injection portion.Thus, the function as a handle was insufficient, and it was difficult todischarge the contents.

In contrast, as shown in the evaluation result in Table 5, in each ofthe flexible packages according to Examples 4-1 to 4-4, the innerpressure of the gas injection portion was not reduced to the extent thatthe upper part of the flexible package hung down, and thus the shaperetaining property was maintained. In the flexible packages according toExamples 4-1 to 4-4, since reduction in the inner pressure of the gasinjection portion was suppressed, the function of the gas injectionportion as a handle was not deteriorated. Even after the preservationperiod has passed, ease of discharging the contents with the gasinjection portion and its vicinity being held was maintained. Inparticular, in the flexible packages of Examples 4-1 to 4-3 in which theoxygen permeability of the non-sealed region was 5 cc/(m²·day·atm),discharge of air immediately after injection of air into the non-sealedregion was not observed, and the inner pressure of the gas injectionportion was maintained at the same level as that immediately after airinjection, whereby the shape retaining property and the function as ahandle were maintained for a long period of time.

(Seal Strength)

Examples 5-2 to 5-5, 5-7, 5-8, and 5-10 to 5-12 and Comparative Examples5-1, 5-6 and 5-9 of the flexible package 100 in which the diameter R ofthe gas injection portion 107 was 8 mm and the length thereof was 180 mmwere produced. In each of Comparative Examples and Examples, the heightwas 280 mm, the width was 180 mm, and the insertion length of the bottomfilm 103 was 50 mm. One gas injection portion 107 was provided in theside edge portion 108. The width of the side edge portion 108 in whichthe gas injection portion 107 was formed was 22 mm. Each of ComparativeExample 5-1 and Examples 5-2 to 5-5 was formed of a film having a layerstructure of PET (polyethylene terephthalate) of 12 μm/aluminum (AL) of9 μm/nylon (NY) of 15 μm/linear low density polyethylene (LLDPE) of 100μm. Each of Comparative Example 5-6 and Examples 5-7 and 5-8 was formedof a film having a layer structure of transparent deposition PET of 12μm/NY of 15 μm/unstretched polypropylene (CPP) of 70 μm. The transparentdeposition PET is a transparent film having barrier property andobtained by vapor-depositing alumina, silicon oxide, or the like on aPET film. Each of Comparative Example 5-9 and Examples 5-10 to 5-12 wasformed of a film having a layer structure of NY of 15 μm/AL depositionPET of 12 μm/LLDPE of 100 μm.

The seal strength of the side edge portion 108 in which the gasinjection portion 107 is formed is 20 N/15 mm in Comparative Examples5-1, 5-6 and 5-9, 30 N/15 mm in Examples 5-2, 5-7 and 5-10, 50 N/15 mmin Examples 5-3, 5-8 and 5-11, 80 N/15 mm in Example 5-12, 100 N/15 mmin Example 5-4, and 150 N/15 mm in Example 5-5. In each of Examples andComparative Examples, presence/absence of gas leakage due to peeling ofseal was checked: at the time of gas injection when the gas injectionportion 107 was formed so that the above-described repelling force was10 N and 30 N at room temperature and 1 atm; at the time of boilingwhen, after formation of the gas injection portion 107, the gasinjection portion 107 was heated for 60 minutes in hot water of 95° C.at 1 atm; and at the time of high-temperature preservation when the gasinjection portion 107 was preserved for one week in air at 60° C. and 1atm. The result is shown in the following Table 6.

TABLE 6 Repelling force Repelling force of gas injection of gasinjection portion 10 N portion 30 N Seal High- High- strength Gas tem.,Gas tem., (N/15 injec- Boil- preser- injec- Boil- preser- mm) tion ingvation tion ing vation Com. 5-1 20 + − − − NA NA Exam. Exam. 5-230 + + + + + + 5-3 50 + + + + + + 5-4 100 + + + + + + 5-5150 + + + + + + Com. 5-6 20 + − − − NA NA Exam. Exam. 5-7 30 + + + + + +5-8 50 + + + + + + Com. 5-9 20 + − − − NA NA Exam. Exam. 5-1030 + + + + + + 5-11 50 + + + + + + 5-12 80 + + + + + +

In Table 6, “+” indicates that no gas leakage occurred, and “−”indicates that gas leakage occurred. In Comparative Examples 5-1, 5-6,and 5-9 in which the seal strength was 20 N/15 mm, no gas leakageoccurred at the time of gas injection, but gas leakage occurred at thetime of boiling and high-temperature preservation. When the repellingforce was 30 N, gas leakage occurred at the time of gas injection, andno gas injection portion 107 was formed. Therefore, evaluations at thetime of boiling and high-temperature preservation could not be performed(NA). In contrast, in each of Examples having the seal strength of 30N/15 mm, in either case where the repelling force was 10 N or 30 N, nogas leakage occurred during any of gas injection, boiling, andhigh-temperature preservation.

When each of Examples and Comparative Example were caused to fall fast,peeling of seal was confirmed in an extremely small part of the sideedge portion 108 in Comparative Example 5-1, Example 5-2, ComparativeExample 5-6, Example 5-7, Comparative Example 5-9, and Example 5-10 inwhich the seal strength was 30 N/15 mm or less, but no peeling of sealoccurred in Examples 5-3, 5-4, 5-5, 5-8, 5-11 and 5-12 in which the sealstrength was 50 N/15 mm or more. Thus, sufficient strength wasconfirmed.

(Shape)

A plurality of blanks similar to the blank 200 shown in FIG. 11 wereproduced in which the width W and the insertion length B of the bottomfilm 103 were varied. In each blank, contents were injected into thestorage part 105, gas was injected into the non-sealed region 106 toform the gas injection portion 107, and the storage part 105 and theslit 111 were sealed, thereby producing a sample of a flexible package.Each sample was evaluated for ease of self-standing and expansion of thebottom film 103. The evaluation result is shown in the following Table7.

TABLE 7 Expan- Over- Ratio W (mm) Self- sion of all (B/ 170 140 110standing bottom evalu- W) B (mm) property film ation Com. 6-1 0.10 17 1411 − ++ − Exam. Exam. 6-2 0.15 26 21 17 + ++ + 6-3 0.20 34 28 22 ++ ++++ 6-4 0.25 43 35 28 ++ ++ ++ 6-5 0.30 51 42 33 ++ ++ ++ 6-6 0.35 60 4939 ++ ++ ++ 6-7 0.40 68 56 44 ++ + + 6-8 0.45 77 63 50 ++ + + Com. 6-90.50 85 70 55 ++ − − Exam. 6-10 0.55 94 77 61 ++ − − 6-11 0.60 102 84 66++ − −

In Table 7, samples corresponding to Examples 6-2 to 6-8 each have theabove-described second feature, whereas samples corresponding toComparative Examples 6-1, 6-9 to 6-11 each do not have the secondfeature. In Table 7, “++” indicates that the evaluation result was good,“+” indicates that the evaluation result was inferior to “++” but waswithin an allowable range, and “−” indicates that the evaluation resultwas not good. In Examples 6-2 to 6-8, the first side-surface film 101and the second side-surface film 102 were sufficiently expanded in acylindrical shape and stably stood up, and the fold line of the bottomfilm 103 was sufficiently extended in the center portion thereof to makethe bottom surface of the storage part 105 flat, and thereby asufficient capacity of the storage part 105 was ensured. In addition,within a range of 0.20≦B/W<0.35, the stability of self-standing and theexpansion of the bottom film were particularly good. In contrast, inComparative Example 6-1 whose ratio of B/W is smaller than those ofExamples 6-2 to 6-8, the first side-surface film 101 and the secondside-surface film 102 were not expanded in a cylindrical shape, and weredifficult to stably stand up. In Comparative Examples 6-9 to 6-11 whoseratios of B/W were larger than those of Examples 6-2 to 6-8, the foldedbottom film 103 was not sufficiently extended and therefore the bottomsurface of the storage part 105 was not made flat, and thus a sufficientcapacity of the storage part 105 could not be ensured.

Further, blanks similar to the blank 120 shown in FIG. 3 were producedin which the distance from the upper end of the non-sealed region 106 tothe upper end of the blank 120 was varied. In each blank, water wasinjected as contents into the storage part 105, and gas was injectedinto the non-sealed region 106 to form the gas injection portion 107,and then the storage part 105 and the slit 111 were sealed, therebyproducing Examples 7-1, 7-2 and 7-5 and Comparative Examples 7-3, 7-6and 7-7 of flexible packages. The height H of each of Examples andComparative Examples was 280 mm, and the width W thereof was 180 mm. Theinsertion length B of the bottom film 103 was 50 mm, and the distance Dfrom the lower end of each flexible package to the lower end of the gasinjection portion 107 was 80 mm. In Examples 7-1 and 7-2 and ComparativeExample 7-3, the distance A from the upper end of the gas injectionportion 107 to the upper end of the flexible package 100 was 60 mm, 80mm, and 100 mm, respectively. Meanwhile, Comparative Examples 7-4 and7-8 were also produced in which water was injected into the blank 120and the storage part 105 was sealed, but no gas injection portion 107was formed. In Examples 7-1 and 7-2 and Comparative Examples 7-3 and7-4, 900 ml of water was injected so that the distance C from the watersurface to the upper end of the flexible package 100 was 80 mm. InExample 7-5 and Comparative Examples 7-6 to 7-8, 1000 ml of water wasinjected so that the distance C from the water surface to the upper endof the flexible package 100 was 65 mm. The respective Examples andComparative Examples were evaluated for ease of retaining theself-standing posture and ease of discharge. The evaluation result isshown in the following Table 8.

TABLE 8 Self- Ease A A/H C standing of dis- (mm) (%) (mm) propertycharge Exam. 7-1 60 21 80 ++ ++ 7-2 80 29 80 ++ ++ Com. 7-3 100  36 80 −− Exam. 7-4 NA NA 80 − − Exam. 7-5 60 21 65 ++ ++ Com. 7-6 80 29 65 − ++Exam. 7-7 100  36 65 − − 7-8 NA NA 65 − −

In Table 8, each of Examples 7-1, 7-2 and 7-5 and Comparative Examples7-3, 7-4 and 7-6 to 7-8 has a B/W ratio of 0.28, and has the secondfeature. Each of Examples 7-1, 7-2 and 7-5 has the fourth feature andthe fifth feature. Comparative Example 7-6 has the fourth feature butdoes not have the fifth feature. Each of Comparative Examples 7-3, 7-4,7-7 and 7-8 do not have the fourth and fifth features. In Table 8, “++”indicates that the evaluation result was good, and “−” indicates thatthe evaluation result was not good. In Examples 7-1, 7-2 and 7-5, it wasconfirmed that, when the upper part of the flexible package 100 wasbent, the flexible package 100 was restored to the original shape, andthe shape was less likely to deform, and thus the self-standing propertywas easily maintained. In Comparative Examples 7-3, 7-4 and 7-6 to 7-8,the upper part of the flexible package 100 was bent and the shape wasdeformed to be easy to fall, and thus the self-standing property was notsufficiently maintained. In Examples 7-1, 7-2 and 7-5 and ComparativeExample 7-6, when water was discharged from the discharge part 104, theupper part of the flexible package 100 was not bent, and the dischargepart 104 can be stably directed to the discharge direction, and thussatisfactory ease of discharge was achieved. However, in ComparativeExamples 7-3, 7-4, 7-7 and 7-8, the upper part of the flexible packagewas bent when water was discharged, and the discharge part 104 could notbe directed in the discharge direction, and thus sufficient ease ofdischarge could not be obtained.

A bottom gusset type flexible package having a large size or including aspout or the like attached to an opening portion is low in rigidity.Therefore, when such a flexible package is displayed or used on a table,an upper portion thereof may be bent to deteriorate appearance of thepackage, or the package may lose the self-standing property and fall.Further, when such a flexible package is held up to discharge thecontents out of the package, the package is likely to bend, andtherefore, it is difficult to hold the package or discharge thecontents. Therefore, an object of the present invention is to solve theabove-described problems by improving the shape retaining property ofthe flexible package, and improving the self-standing property thereof.

In order to solve the above problems, the present invention provides aflexible package in which at least a first side-surface film and asecond side-surface film are joined together, and peripheral portions ofthe films are sealed to form a storage part. On one or both of two sideedge portions which are sealed regions of the peripheral portions atboth side ends of the first side-surface film and the secondside-surface film, a non-sealed region is provided which is a region inwhich the first side-surface film and the second side-surface film arenot sealed over a predetermined length. The non-sealed region issurrounded by the sealed regions of the first side-surface film and thesecond side-surface film. In the non-sealed region, a gas injectionportion is formed in which a gas whose specific heat at constant volumeis 0.67 kJ/kg-deg or higher at 0° C. and 1 atm. The gas injectionportion has a diameter not smaller than 3 mm but not larger than 50 mm.A repelling force measured when the entirety of the gas injectionportion is nipped from the first side-surface film side and the secondside-surface film side and squeezed until the width of the nipped gasinjection portion becomes half the diameter of the gas injectionportion, is not smaller than 4 N but not larger than 30 N at 23° C. and1 atm.

Further, the flexible package further includes a bottom film which isfolded in half and inserted, from a fold line side, between the firstside-surface film and the second side-surface film, and has a sealedperipheral portion. A loop stiffness of the first side-surface film andthe second side-surface film in a direction corresponding to a verticaldirection when the flexible package is made to stand by itself with thebottom film side as a bottom surface, is not smaller than 30 mN but notlarger than 1300 mN. A loop stiffness of the first side-surface film andthe second side-surface film in a direction corresponding to ahorizontal direction when the flexible package is made to stand byitself, is not smaller than 20 mN/25 mm (width) but not larger than 1200mN/25 mm (width).

The non-sealed region may have an oxygen permeability equal to or lowerthan 30 cc/(m²·day·atm) at 20° C. and 60%.

The side edge portions each may have a seal strength equal to or largerthan 30 N/15 mm.

A distance from an upper end of the non-sealed region to an upper end ofthe flexible package may be equal to or smaller than 30% of a height ofthe flexible package.

In the side edge portions, a cut guide portion may be formed at aposition near the gas injection portion so as to extend from theposition to the gas injection portion. The cut guide portion guidescutting of the first side-surface film and the second side-surface film.

According to the present invention, it is possible to provide a flexiblepackage including a gas injection portion which improves self-standingproperty and portability of the flexible package.

The present invention is useful for flexible packages and the like.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. A flexible package, comprising: a firstside-surface film, a second side-surface film, and a bottom film whichare joined together, the bottom film being inserted between the firstside-surface film and the second side-surface film so as to be folded inhalf and inserted from a fold line side, with a predetermined insertionlength; and a storage part formed by sealing peripheral portions of thefilms, the storage part having a lower bottom surface which is thebottom film, wherein on one or both of two side edge portions which aresealed regions of the peripheral portions at both side ends of the firstside-surface film and the second side-surface film, a non-sealed regionis provided which is surrounded by the sealed regions of the firstside-surface film and the second side-surface film and is not sealedover a predetermined length, in the non-sealed region, a gas injectionportion is formed so as to contain a gas whose specific heat at constantvolume is 0.67 kJ/kg·deg or higher at 0° C. and 1 atm, the gas injectionportion has a diameter not smaller than 3 mm but not larger than 50 mm,a repelling force measured when the entirety of the gas injectionportion is nipped from the first side-surface film side and the secondside-surface film side and squeezed until the width of the nipped gasinjection portion becomes half the diameter of the gas injectionportion, is not smaller than 4 N but not larger than 30 N at 23° C. and1 atm, the non-sealed region has an oxygen permeability equal to orlower than 30 cc/(m2·day·atm) at 20° C. and 60% RH, the side edgeportions each have a seal strength equal to or larger than 30 N/15 mm, aloop stiffness of the first side-surface film and the secondside-surface film in a direction corresponding to a vertical directionwhen the flexible package is made to stand by itself is not smaller than30 mN/25 mm (width) but not larger than 1300 mN/25 mm (width), and aloop stiffness of the first side-surface film and the secondside-surface film in a direction corresponding to a horizontal directionwhen the flexible package is made to stand by itself, is not smallerthan 20 mN/25 mm (width) but not larger than 1200 mN/25 mm (width). 2.The flexible package according to claim 1, wherein in the side edgeportions, a cut guide portion to guide cutting of the first side-surfacefilm and the second side-surface film is formed at a position near thegas injection portion so as to extend from the position to the gasinjection portion, the cut guide portion being at least one slitextending in a top-bottom direction and penetrating the firstside-surface film and the second side-surface film.
 3. The flexiblepackage according to claim 2, wherein in at least one of the firstside-surface film and the second side-surface film, an indication thatindicates the position of the cut guide portion is provided on or nearthe cut guide portion.
 4. The flexible package according to claim 2,wherein the cut guide portion is a cross-shaped slit which is formed ata position within 15 mm upward from an upper end of the gas injectionportion, and is composed of a slit extending in the top-bottomdirection, and a slit extending in a left-right direction andpenetrating the first side-surface film and the second side-surfacefilm, and the slit extending in the top-bottom direction and the slitextending in a left-right direction each have a length not smaller than1 mm.
 5. The flexible package according to claim 1, further comprising:a sealed spout sandwiched between the first side-surface film and thesecond side-surface film.